This invention is a switchable radioactive neutron source device. It can provide a controllable ON or OFF generation of neutrons or a coded pulsed generation of neutrons by a sequence of switching. This neutron source device has various present and potential applications both in scientific research and in inspection and analysis techniques.
Current neutron source devices are of two types: the standard radioiosotope source and the accelerator source. The standard radioisotope source employs a radioactive mixture of alpha emitter and target material which emits neutrons constantly. Therefore, it must be extensively shielded to protect operating personnel even when not in use. The accelerator neutron source requires bulky equipment, considerable electric power, and highly trained operating personnel, yet provides low reliability and maintainability.
In applications involving inspection of a sample for content of fissile material, a standard neutron source is used for irradiation of a sample, after which a count is made of delayed neutrons from fissionable isotopes in the samples. Typically, an object to be analyzed is shuttled into the presence of the radioisotope source from a remote shielded area and back again.
A potential application employing neutron irradiation is the detection of explosive materials attempted to be smuggled onto aircraft. High explosives tend to be rich in nitrogen, and so a possible detection scheme would have a suitcase on a conveyor belt passing through a neutron flux long enough for it to be tested for the presence of an unusual amount of nitrogen. Possible gamma ray detection techniques for this purpose include spectral analysis of prompt gamma rays from neutron capture or from inelastic neutron scattering or of decay gammas from neutron activation.
Other potential applications include nondestructive testing and subcriticality monitoring.
It is therefore an object of this invention to provide a reliable neutron source device that can be switched ON for use and OFF when not in use to eliminate costly shielding.
It is a further object of this invention to provide a neutron source that is portable and easy to use.
It is still a further object of this invention to provide a neutron source that can be pulsed at predetermined intervals for detection techniques that use time-coded sources.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.